The present invention relates to the treatment of ailments in humans and other mammals, and more particularly, to an improved method and apparatus for the application of controlled electric fields for in vivo delivery of genes and pharmaceutical compounds into live cells of a patient by electroporation.
In the 1970's it was discovered that electric fields could be used to create pores in cells without causing permanent damage to them. This discovery made possible the insertion of large molecules into cell cytoplasm. It is known that genes and other molecules such as pharmacological compounds can be incorporated into live cells through a process known as electroporation. The genes or other molecules are mixed with the live cells in a buffer medium and short pulses of high electric fields are applied. The cell membranes are transiently made porous and the genes or molecules enter the cells. There they can modify the genome of the cell.
Electroporation has been recently suggested as one approach to the treatment of certain diseases such as cancer. For example, in the treatment of certain types of cancer with chemotherapy it is necessary to use a high enough dose of a drug to kill the cancer cells without killing an unacceptable high number of normal cells. If the chemotherapy drug could be inserted directly inside the cancer cells, this objective could be achieved. Some of the best anti-cancer drugs, for example, bleomycin, normally cannot penetrate the membranes of certain cancer cells. However, electroporation makes it possible to insert the bleomycin into the cells.
One therapeutic application of electroporation is for cancer treatment. Experiments on laboratory mammals have been carried out and reported as follows: Okino, M., E. Kensuke, 1990. The Effects of a Single High Voltage Electrical Stimulation with an Anticancer Drug on in vivo Growing Malignant Tumors. Jap. Journal of Surgery. 20: 197-204. Mir, L. M., S. Orlowski, J. Belehradek Jr., and C. Paoletti. 1991. Electrochemotherapy Potentiation of Antitumor Effect of Bleomycin by Local Electric Pulses. Eur. J. Cancer. 27: 68-72. Clinical trials have been conducted and reported by Mir, L. M., M. Belehradek, C. Domenge, S. Orlowski, B. Poddevin, et al. 1991. Electrochemotherapy, a novel antitumor treatment: first clinical trial. C.R. Acad. Sci. Paris. 313: 613-618.
This treatment is carried out by infusing an anticancer drug directly into the tumor and applying an electric field to the tumor between a pair of electrodes. The field strength must be adjusted reasonably accurately so that electroporation of the cells of the tumor occurs without damage, or at least minimal damage, to any normal or healthy cells. This can normally be easily carried out with external tumors by applying the electrodes to opposite sides of the tumor so that the electric field is between the electrodes. The distance between the electrodes can then be measured and a suitable voltage according to the formula E=V/d can then be applied to the electrodes (E=electric field strength in V/cm; V=voltage in volts; and d=distance in cm). When internal tumors are to be treated, it is not easy to properly locate electrodes and measure the distance between them. In the aforementioned parent application, there is disclosed a system of electrodes for in vivo electroporation wherein the electrodes may be inserted into body cavities. In a related U.S. Pat. No. 5,273,25 a syringe for injecting molecules and macromolecules for electroporation utilizes needles for injection which also function as electrodes. This construction enables the subsurface placement of electrodes. It would be desirable to have an electrode apparatus having electrodes that can be inserted into or adjacent tumors so that predetermined electric fields can be generated in the tissue for electroporation of the cells of the tumor.
Studies have also shown that large size nucleotide sequences (up to 630 kb) can be introduced into mammalian cells via electroporation (Eanault, et al., Gene (Amsterdam), 144(2):205, 1994; Nucleic Acids Research, 15(3):1311, 1987; Knutson, et al., Anal. Biochem., 164:44, 1987; Gibson, et al., EMBO J., 6(8):2457, 1987; Dower, et al, Genetic Engineering, 12:275, 1990; Mozo, et al, Plant Molecular Biology, 16:917, 1991), thereby affording an efficient method of gene therapy, for example.